Different From vs. Different Than

Once I read in a grammar book that "different from" was more grammatically correct than "different than," and since then I have always been using "different from" in my sentences.

However, I have noticed that many people around me—including my English teacher—prefer to use "different than, " and this has led to me wanting to find out what is actually correct. ---

From what I have read in the Internet, some people think that both usages are fine, while most of the others agree that "different from" is the grammatically correct way, and that "different than" is less formal or is improper.

I will post the clearest explanation that I have found:

"Differ" takes the preposition from (exclusively), for the simple and logical reason that, as the verb "to defer" implies, it sets apart by exclusion rather than by degree of comparison. As in – This is different from that. When something differs, it implies another, from which it is distinguished. 

The fundamental question: How does something, be it a state of being, a quality, a quantity, an action,…differ from another thing? Answer, comparatively, by contrast. The contrast is either by degree, or by total exclusion; if one thing is excluded (outside the set which includes another) from, it is different. The preposition "than" is used with greater or less; the preposition, "from" is used with different.

Taken from a comment in: http://data.grammarbook.com/blog/adjectives-adverbs/different-from-vs-different-than/

Yay, another question solved. :)